1. Field of the Invention
The present invention relates to center special slotted containers, and in particular to center special containers adapted to be assembled in folder-gluer machines.
2. Prior Art
In the manufacture of containers, and in particular fibreboard containers, it is desirable to automate the process as fully as possible in order to reduce costs. Container manufacturers utilize "folder-gluer" machines which receive a box blank in a hopper, fold the blank to form an intermediate blank or "knocked down" container, align or "square up" the blank at a squaring station so that the panels on either side of the joint are aligned, and apply adhesive to the joint to seal the ends of the blank to each other. Such folder-gluer machines are well known in the art.
After adhesive has been applied to the manufacturer's joint in the folding and gluing process, pressure is applied to the joint, usually by rollers, to aid in the sealing of the joint. Prior to the rolling operation and before the adhesive applied to the joint sets up, the folded blank is aligned or "squared up" in a squaring section of the folder-gluer machine. The squaring action may be effected by a pair of opposing vertically disposed platens which contact opposing edges of the folded blank defined by the flaps of the container. In order for the spanking action of the platens to square-up the folded blank effectively, it is necessary that the flaps on both sides of the folded blank be of the same length; otherwise the panels from which the flaps extend will become misaligned as a result of the spanking action and the resultant knocked down blank will be of unacceptable quality.
Accordingly, box blanks used to form regular slotted containers are ideally suitable for use with a folder-gluer machine. A regular slotted container is one in which all of the flaps are the same length. Usually, the flaps are of a length such that the lengthwise flaps -- that is, the flaps extending from the front and rear side panels of the box -- are approximately one-half the length of the end panels so that, when folded, the flaps meet to abut at the center of the box forming a cube.
However, in regular slotted containers which have sides which are not square but rather rectangular, the flaps extending from the end panels, which form the inner flaps of the box, do not abut each other and the container has uneven top and bottom surfaces resulting from the gap between the end flaps. Where it is necessary to provide a slotted container having an even top and/or bottom surface, such as when small containers of food are packed, fill-in pads are provided and are positioned in the gap between the folded inner flaps of the top and bottom surfaces of the box. Another method of providing a flat top or bottom surface is to provide a pad that is inserted into the set up container and covers the entire top or bottom surface of the box. A disadvantage with the use of all such pads is that the cost of the container is increased as a result of the necessity of adding additional pieces to the box and an additional step in the packing of the box in which the pad or pads is placed in the box prior to its being loaded with the items to be packaged.
An alternative container which provides an even top and bottom surface is the center special slotted container. The center special slotted container is similar to the regular slotted container previously described except that the inner flaps which extend from the end panels extend outwardly from the end panels a distance equal to approximately one-half the length of the front and rear side panels so that they meet at the center of the box. The inner flaps thus provide a level rest for the contents of the box without the use of pads. In addition, the center special slotted container is stronger at the top and bottom due to the double thickness of fibreboard in these areas.
However, for certain shapes of blanks, a disadvantage with the center special slotted container is that it is not adapted to be formed in a folder-gluer machine. For example, a blank for a non-square center special slotted container has cover flaps extending from the front and rear side panels which are shorter in length than those extending from the end panels. The blank as presently made consists of four panels: front and rear side panels, an end panel joining the side panels, and a second end panel attached to a side panel opposite the first end panel. The second end panel includes a tab which is overlapped by the end of the noncontiguous side panel when the blank is folded. When processed by a folder-gluer machine, the slapping action of the platens at the squaring station cannot properly align the panels of the folded blank so that the resultant knocked down container is properly squared, since the platens cannot contact both of the panels that overlap to form the joint. As a result, manufacturers who utilize folder-gluer machines to manufacture folded blanks for non-square center special slotted containers experience a high rate of rejection resulting from misalignment of the panels of the container.
Therefore, there is a need for a box blank which can be formed into an intermediate folded blank for a non-square center special slotted container which is adapted to be utilized by a folder-gluer machine without yielding a high rate of rejection. In addition, there is a need for a non-square center special slotted container which is inexpensive to fabricate and does not require additional pieces and the addition of steps in the formation of a box from a blank.